X and s charts for health care comparisons.

In previous articles [M.K. Hart, Qual Manage Health Care. 2004;13(2):99-119 and 2003;12(1):5-19], the author presented control charts applicable for risk-adjusted, time-ordered variables and attribute data. The present article uses Shewhart X and s charts with risk-adjusted variables data to compare length-of-stay data from several healthcare organizations. The comparisons are made on the data both before and after risk adjustment, enabling the impact of risk adjustment to be readily determined.